The invention relates to a transfer bar lift apparatus for use with systems requiring a vertical lift capability to move a workpiece between a first position and a second position, such as with a lift and carry transfer machine.
Transfer bar lift devices typically are used in machining operations where there are a number of stations between which a workpiece is cycled in order to receive different machining operations at each station. The workpiece can be moved directly by the transfer bar, or the workpiece can be secured to a pallet which is moved by the transfer bar. In either case, the workpiece is supported by the transfer bar and the transfer bar moves forward a prescribed distance during each step between the stations. Usually, the transfer bar is configured as two members in side-by-side relation to one another. When the transfer bar finishes the horizontal motion, the workpiece is placed in a stationary fixture which supports the workpiece for machining operations, or as a temporary transfer fixture for further movement along the path of travel. Before the transfer bar moves horizontally, it is raised vertically to lift the workpiece from the fixture prior to horizontal transportation. The lifting motion for the transfer bar is typically accomplished by lift arms and typically requires a distance of approximately seven inches for sufficient clearance for the horizontal movement.
Presently known lift devices require complex lift arm linkage mechanisms in order to operate properly. These devices and the numerous pivoting connections required for proper operation are subject to wear and failure problems when used in typical industrial environments. It would be desirable to provide a simplified lift device having fewer pivoting joints. It would be desirable to provide a lift apparatus where the prime mover, such as a motor or actuator, can be positioned in a location less prone to contamination and processing byproduct infiltration into the movement mechanism. It would be desirable to provide a lift apparatus capable of being configured with a variety of lift distances and lift motions without substantial changes to the actuator mechanism. It would be desirable to provide a lift apparatus having the capability of incorporating at least one dwell position and/or at least one detent or fail safe lock position. It would be desirable to provide a lift apparatus that could be mounted entirely on top of the machine bases to allow for future xe2x80x9cabove floor coolant systemsxe2x80x9d.
The present invention provides a lifting mechanism having a cam surface and cam follower, such as a cam and slot configuration. The cam surface or slot can be formed in a wide variety of configurations to provide the lifting force to a transfer bar when driven in a horizontal direction by an actuator. The lift mechanism requires less horsepower, less space, and is easier to service and replace than previous configurations. The drive mechanism is not located in the area prone to contamination from work station processing. In addition, the cam surface or slot can potentially be configured into a cradle position eliminating the need for a separate locking pin to hold the elevator transfer bar in the raised position. The cam surface or slot generally extends along an inclined path with a cam follower disposed in operable engagement with the cam surface in order to move the transfer bar vertically between raised and lowered positions as the cam follower moves between a first end limit of travel and a second end limit of travel. Alternative configurations can be provided to the shape and contour of the cam surface or slot in order to provide a self-locking rest position in the upper and/or lower positions, and/or at least one intermediate dwell position or the like.
An apparatus for elevating a part according to the present invention includes a transfer bar movable between a first position and a second position. A support member is provided having a cam surface with a first end and a second end. A cam follower is engageable with the cam surface and supports the transfer bar with respect to the support member. The cam follower is movable between the first end and the second end of the cam surface, so that the transfer bar is in the first position when the cam follower is adjacent the first end of the cam surface, and the transfer bar is in the second position when the cam follower is adjacent the second end of the cam surface. Means is provided for driving the cam follower between the first and second ends of the cam surface. The driving means can include any suitable prime mover, such as a motor, or actuator, either electric, hydraulic, or pneumatic, or other suitable substitute. The cam surface can include a non-linear surface portion. The non-linear surface portion can include a cradle position, or a lock position, and/or one or more intermediate dwell positions or the like.
Other objects, advantages and applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.